"Did you mean?" feature in Lucene.net

You should look into the SpellChecker module in the contrib dir. It's a port of Java lucene's SpellChecker module, so its documentation should be helpful.

(From the javadocs:)

Example Usage:

  import org.apache.lucene.search.spell.SpellChecker;

  SpellChecker spellchecker = new SpellChecker(spellIndexDirectory);
  // To index a field of a user index:
  spellchecker.indexDictionary(new LuceneDictionary(my_lucene_reader, a_field));
  // To index a file containing words:
  spellchecker.indexDictionary(new PlainTextDictionary(new File("myfile.txt")));
  String[] suggestions = spellchecker.suggestSimilar("misspelt", 5);

AFAIK Lucene supports proximity-search, meaning that if you use something like:

field:stirng~0.5

(it s a tilde-sign)

will match "string". the float is how "tolerant" the search would be, where 1.0 is exact match and 0.0 is match everything (sort of).

Different parsers will however implement this differently.

A proximity-search is much slower than a fuzzy-search (stri*) so use it with caution. In your case, one would assume that if you find no matches on a regular search, you try a proximity-search to see what you find, and present "did you mean" based on the result somehow.

Might be useful to cache this sort of lookups for very common mispellings, for performance reasons.